Dull finish laminated drawing board cover



Oct. 22, 1957 H. FLETCHER; JR 2,810,232

nuu. FINISH LAMINATED DRAWING BOARD COVER Filed Nov. 12, 195$v 2 Sheets-Sheet l JNVENTOR. g HORACE FLETCHER Jr.

Oct. 22. 1957 H. FLETCHER, JR DULL FI NISH LAMINATED DRAWiNG BOARD COVER Filed Nov. 12 1953 2 Sheets-Sheet 2 v INVENTORI HORACE FLETCHER Jr.

RNEY

United States Patent DULL FINISH LAMINATED DRAWING BOARD COVER Horace Fletcher, Jr., Montville, N. J.

Application November 12, 1953, Serial No. 391,480

4 Claims. (Cl. 45131) This invention relates to a drawing board cover in the form of sheet material which may be applied to a drawing board to cover up imperfections in the wooden board including the grain of the wood which the pencil might therwise tend to follow. The cover is relatively inexpensive and when it becomes marred is readily replaced, thereby increasing the life of the board itself.

The type of drawing board cover to which the present invention pertains is disclosed in Patent No. 2,327,963 of August 24, 1943 to S. Ward Haas and other advantages of this type of cover are fully described therein. The present cover is an improvement over the cover described in the patent. It has long been recognized that the reflection qualities of the prior art cover were objectionable. The shiny surface of the prior art cover reflects light in a manner which can be very annoying to the draftsman adding to the already heavy burden placed upon his eyes and contributing to his general mental fatigue. This was apparently realized to some degree even in 1940 when the patent was written, because on page 2, column 2, lines 37-40 of the patent, it is suggested that the cover might be provided with a dull finish.

However, a satisfactory commercial means and method of accomplishing the long desired result were not achieved until the present invention. When ordinary dull or matte finishes were applied to the surface of the prior art cover it was found that dirt adhered to the cover which quickly made the cover unsightly and furthermore the dirt transferred to the back of the drawing and even to the front of the drawing via the draftsmans hands or his instruments. Such dirt and also pencil markings and the like could not be wiped off the cover provided with an ordinary matte surface so one of the most important advantages of the cover as set forth in the patent was lost when an ordinary matte surface was applied.

Difficulties were also encountered in trying to devise a practical commercial method for providing a matte surface on the drawing cover. The cover is made from a plastic foil laminated to a paper backing by means of a thermoplastic adhesive. When trying to emboss a dull surface on the sheet as suggested in the patent it was found that if sufficient heat was applied to emboss the plastic foil, the thermoplastic adhesive became fluid and was absorbed into the fibers of the paper backing freeing the plastic foil from the paper so that the plastic foil blistered off the paper base.

These problems have now been solved and a drawing cover can now be produced commercially which has a very fine matte surface which does not annoy the draftsman with reflections, which does not pick up dirt and which can be wiped perfectly clean even of pencil markings with an ordinary rag.

The above objects of the invention and the means and method of their attainment will be more fully understood after reading the following description in connection with the drawing, in which:

Fig. I is a view in perspective showing a drawing board base 11.

'Patented Oct. 22, 1957 to which the drawing board cover of the invention is applied and on which a drawing is superimposed;

Fig. II is a fragmentary view showing the laminated drawing board cover, part of the laminations being separated to show details of construction;

Fig. III is a fragmentary view in enlarged sectional elevational showing the laminated drawing board cover.

Fig. IV is a diagrammatic view illustrating the method used for manufacturing the drawing board cover of the present invention.

7 Fig. V is a diagrammatic view illustrating the manner in which a heated roller imbeds into the surface of the plastic foil to provide the special non-glare surface of the present invention.

In Fig. I, the usual wooden drawing board or table 4 is shown covered with the composite drawing board cover 5. While in practice, the cover sheet 5 will be preferably coextensive with the drawing board 4, it has been illustrated as of slightly smaller area for clarity of illustration. As shown in Figs. II and III, the cover 5 is made up of a layer of plastic foil preferably of the cellulose ester type, cellulose acetate having been found to give the best results in practice and having the additional advantage over cellulose nitrate that it is noninflammable. The plastic foil 7 is superimposed upon and laminated to a paper sheet 11 by an adhesive 9 which in combination with the fibrous paper sheet provides a slightly cushioning effect. Cellulose acetate commercially known as #88 P903, which is a plasticized sheet .00088 inch in thickness, has been found satisfactory. It will be evident, however, that somewhat thicker or slightly thinner sheets of the transparent lamination may be employed provided the important characteristics herein set forth are retained.

The base paper sheet has relatively little if any grain, the fibers being arranged in substantially all directions and any possible grain that might have been found in the paper sheet is completely neutralized insofar as it might have any influence in directing a pencil or other drawing instrument by the amorphous foil laminated thereon.

It has been found that if the indentations 13 in the surface of the plastic foil 7, provided to diffuse the light from the foil are not deeper than .0001 of an inch and if the change from the high to low areas of the surface is smooth as accomplished by using the process hereinafter described, these indentations also will not have influence in directing the course of a pencil and furthermore, these indentations will not hold any dirt such as dust, pencil lead, erasures, finger marks and the like and that all such foreign matter can be readily wiped OE With an ordinary rag.

The adhesive layer 9 is highly plasticized to provide the cushioning effect referred to above and to provide a resilient bond between the plastic foil 7 and the paper Sheets made by coating a layer of plastic from solution onto a paper base or by fusing a plastic foil directly to paper base would not be suitable because such sheets crack when sharply folded whereas the material made with the layer of adhesive sandwiched between the plastic foil and the paper backing can be repeatedly creased and uncreased without cracking.

The patent discloses that color may be incorporated into the drawing board cover by using a colored paper backing sheet. However, it is desirable to obtain such color by adding pigment to the adhesive layer. By using this means it is possible to obtain a perfectly uniform colored surface for example of pale green which forms an ideal neutral background for the drawing board. In fact, it is preferred to use suflicient pigment in the adhesive to completely hide the fibers of the paper in order to accomplish the desired uniform neutral background effect.

board cover is illustrated in Fig. IV. The plastic foil 7, preferably cellulose acetate as described, is passed from a feed roll 22 over a transfer roll 24 which transfers the adhesive solution from the pan '26 to the surface of the plastic foil" 7. The doctor roller 25 controls the amount of adhesive which is transferred to the paper 7 by the roller 24. For this purpose, the distance between the rollers 24 and 25 is micro-adjustable. It is important that the adhesive solution does not effect the plastic foil 7. This may be assured by using solvents for the adhesive which are non-solvents for the plastic foil. In the case of a cellulose acetate foil, aromatic hydrocarbon solvents such as toluene and Xylol may be used, but alcohol, ketone and ester solvents are to be avoided. The solvents used in the adhesive solution may also not actually be solvents for the resins used in the adhesive which are preferably thermoplastic vinyl resins. In that event, the adhesive solution is technically not a true solution but an organosol or dispersion of resin particles in the organic solvent. If a pigment is incorporated in the adhesive, the pigment particles will also be founddispersed in the organosol. The solvents are evaporated by passing the coated paper sheet through a heated drying tunnel 27 leaving a layer of thermoplastic adhesive on the plastic foil.

The paper sheet 11 is then brought into contact with the adhesive coated side of the foil 7 and both pass together between pressure rollers. The roller 28 is of steel and is heated. The roller 30 is preferably rubber covered in order to insure even pressure. The temperature of the heated roller 28 is controlled in order to insure sutficient softening of the thermoplastic resin but without permitting it to be absorbed into the paper and Without causing undue softening of the plastic foil. The pressure is also accurately controlled in order to assure the optimum penetration of the thermoplastic adhesive into the fibers of the paper at the particular temperature used.

The laminated sheet then passes between a second pair of pressure rollers. The steel roller 32, which ongages the free surface of the laminated plastic foil, is provided with a very fine matte surface made up of indentations which are not clearly distinguishable under a microscope (IOOX) and certainly no greater than .0001 of an inch deep. After much experimentation, it has been found that a satisfactory surface can be produced by rubbing down the steel roller with No. 150 aluminum oxide paper. The steel roller 32. is electrically heated and when cellulose acetate #88 P903 is used the temperature of this roller is electronically controlled between 150 and 154 C. This temperature was determined experimentally and is very critical. A different temperature would be required. if a different type of plastic foil were used. This temperature might also depend on other factors such as the pressure applied between the rollers. The pressure applied by means of the rubber covered roller 34 is about 100 lbs. per inch length of the contacting rollers. This is about the maximum pressure which can be used if the rubber roller is driven by the steel roller through the laminated material without causing wrinkling of the material. However, if both rollers were independently driven at the same peripheral speed, even higher pressures might be possible. Under the conditions given, the surface of the plastic foil becomes just soft enough to fiow smoothly into the indentations provided in the roller 32. Under the proper conditions, the surface produced on the plastic is smoother than the surface of the roller; i. e., the plastic is not soft enough to follow abrupt indentations accurately as shown schematically in Fig. V. This assures that the finished cover will not pick up and hold dirt. The temperature of the roller 32 is necessarily higher than the temperature of the roller 28 but the temperature is not so high that the adhesive would become fluid enough during the short time the laminated material is in contact with the roller to penetrateinto the fibers of the paper and cause blistering of the plastic foil. The completed drawing board cover with the improved nonglare surface is wound up on the roller 36.

While shown schematically as one continuous process, it is possible to produce the complete material by two or three continuous processes. For example, the plastic foil may be coated with the adhesive and wound up on a roller using a suitable interleaving material. At a later time, the coated foil may be brought into contact with a paper sheet in a different apparatus and the laminated material again wound up on a roller. Finally, at a different time and in a third apparatus, the laminated material may be passed between pressure rollers to provide the special light-diifusing smooth surface as described above.

Surprisingly, it is not practicable to combine the step of laminating the foil to the paper and the step of providing the special non-glare surface in one operation. When brought into contact with the paper sheet, the plastic foil must be under sufficient tension to eliminate all wrinkles and the like. When heated to the necessary temperature as described above, the foil is sufficiently weakened to cause it toseparate under this tension.

The temperature of the roller 32 has been given for the case where the plastic foil is cellulose acetate No. 88 P903. It should be realized that if other plastic foils are used, even other cellulose acetate foils, a different temperature will be required and this temperature will have to be determined experimentally according to the teachings set forth above.

Having thus described the invention, what is claimed is:

1. A sheet for a drawing board cover comprising a paper backing to be mounted against the drawing board, a clear cellulose acetate foil forming a hard smooth sur face upon which the drawing is mounted and a layer of highly plasticized thermoplastic vinyl adhesive sandwiched between said paper backing and said cellulose acetate foil holding said paper backing and said cellulose acetate foil firmly together over their entire area and forming a resilient cushion for the drawing pencil, said adhesive including sufficient pigment to completely hide the fibers of the paper backing, said cellulose acetate foil having a very fine matte surface formed of smooth indentations not visible under times magnification and no more than .0001 of an inch deep diffusing the light reflected from the cover but not sufficiently deep to hold dirt, in cross-section, said indentations changing gradually in depth and following smooth curves.

2. An apparatus for forming a sheet for a drawing board cover comprising a roller for carrying a roll of clear plastic foil, a coating roller disposed to deposit a layer of thermoplastic adhesive onto the clear plastic foil as it is removed from said carrying roller, said coating roller being in contact with a reservoir of said thermoplastic adhesive, a second carrying roller carrying a roll of paper, a pair of pressure rollers, means guiding paper from its carrying roller and said coated plastic foil into contact with each other so that the side of said plastic foil which is coated with said thermoplastic adhesive is in contact with said paper and passing said paper and plastic sheet together between said pressure rollers, at least one of said rollers being heated to a temperature high enough to soften said thermoplastic adhesive sufficiently to cause it to bond to the paper without softening the plastic foil, a second pair of pressure rollers, means guiding the bonded paper and plastic foil between said second pair of pressure rollers under tension, the one of said second pair of pressure rollers which contacts the surface of the plastic foil being provided with a very fine matte surface having indentations no more than .0001 of an inch deep and being maintained at a very accurately controlled temperature higher than used on said first pair of pressure rollers and high enough to soften the plastic foil sutficiently so that the matte surface of the roller is impressed therein Without causing blistering of the foil from the paper and a receiving roller for receiving the finished sheet.

3. An apparatus for forming a sheet for a drawing board cover comprising a roller for carrying a roll of clear cellulose ester foil, a coating roller disposed to deposit a layer of thermoplastic adhesive onto the clear cellulose ester foil after it is removed from said carrying roller, said coating roller being in contact with a reservoir of said thermoplastic adhesive, a second carrying roller carrying a roll of paper, a pair of pressure rollers, means guiding paper from its carrying roller and said coated cellulose ester foil into contact with each other so that the side of said cellulose ester foil which is coated with said thermoplastic adhesive is in contact with said paper and passing said paper and cellulose ester foil together between said pressure rollers, at least one of said rollers being heated to a temperature high enough to soften said thermoplastic adhesive suificiently to cause it to bond to the paper without softening the cellulose ester foil, a second pair of pressure rollers, means guiding the bonded paper and plastic foil between said second pair of pressure rollers under tension, the one of said second pair of rollers which contacts the surface of the cellulose ester foil being provided with a very fine matte surface obtained by rubbing with an abrasive sheet at least as fine as No. 150 aluminum oxide paper and maintained at a very accurately controlled temperature higher than used on said first pair of rollers and high enough to soften the cellulose ester foil sufiiciently so that the matte surface of the roller is impressed therein without causing blistering of the foil from the paper and a receiving roller for receiving the finished sheet.

4. An apparatus for forming a sheet for a drawing board cover comprising a roller for carrying a roll of clear cellulose acetate foil, a coating roller disposed to deposit a layer of highly plasticised thermoplastic vinyl adhesive onto the clear cellulose acetate foil after it is removed from said carrying roller, said coating roller being in contact with a reservoir of said highly plasticized thermoplastic viynl adhesive, a second carrying roller carrying a roll of paper, a pair of pressure rollers, means guiding paper from its carrying roller and said coated cellulose ester foil into contact with each other so that the side of said cellulose ester foil which is coated with said highly plasticized thermoplastic vinyl adhesive is in contact with said paper and passing said paper and cellulose acetate foil together between said pressure rollers, at least one set of rollers being heated to a temperature high enough to soften said thermoplastic adhesive sufliciently to cause it to bond to the paper without softening the plastic foil, a second pair of pressure rollers, means guiding the bonded paper and plastic foil between said pair of pressure rollers under tension, the one of said second pair of rollers which contacts the surface of the cellulose acetate foil being provided with a very fine matte surface obtained by rubbing with an abrasive sheet at least as fine as No. aluminum oxide paper and maintained very accurately between the temperatures of 150154 C. which is just high enough to soften the cellulose acetate foil sufiiciently so that the matte surface of the roller is impressed therein without causing blistering of the foil from the paper and a receiving roller for receiving the finished product.

References Cited in the file of this patent UNITED STATES PATENTS 2,218,227 Winnek Oct. 15, 1940 2,318,111 Steinberger May 4, 1943 2,327,963 Haas Aug. 24, 1943 2,442,598 Harrison June 1, 1948 

